The regulation, a provision of last year's federal Deficit Reduction Act, has had a much greater effect on low-income U.S. citizens than the immigrants it is trying to block, Maryland health policy advocates say.

In the past, Medicaid applicants signed a sworn statement attesting to their citizenship and no additional proof was required. Now they must provide documents to prove both citizenship and identity.

Last month, for example, Gloria Gann, a single mother in Dundalk, submitted new applications to the Maryland Children's Health Insurance Program for her two children. Her 13-year-old son was accepted, but her 15-year-old daughter was turned down because of improper documentation.

Gann will have to reapply after gathering a host of records from her daughter's doctor, school and the Social Security Administration.

"When you go down to Social Security, they want you in there for four or five hours," said Gann. "That's a lot of running around and I work five days a week."

Gann, 40, makes $9,000 or $10,000 annually as a bar maid in Baltimore's Greektown. She doesn't drive and has no phone at home, so getting around is extremely difficult, she said over the phone from work, between waiting on customers.

Gann wishes that someone had explained the document requirements when she first applied.

"If I didn't really need it so bad, I'd say forget it," she said.

She's not alone in her frustration.

Advocates for low-income children, legal immigrants and the homeless say they are concerned because the new regulations add barriers to health care for people already struggling to make ends meet.

Although the law was designed to prevent non-citizens from getting Medicaid, this hasn't been a widespread problem, said Patricia Hatch, program manager for the Maryland Office for New Americans.

Centers for Medicare & Medicaid Services Administrator Mark B. McClellan found that there was "little evidence that many non-eligible, non-citizens are receiving Medicaid," according to a 2005 study by the Department of Health and Human Services.

The state says it can't do anything about the complaints.

Maryland must comply with the new requirements, said Charles Lehman, executive director for eligibility at the Maryland Department of Health and Mental Hygiene. "I can't break the law."

To make sure clients are aware of the changes, the state has sponsored town hall meetings in seven counties, established a multi-lingual hotline to address questions and sent letters to Medicaid clients up for renewal.

Still, the majority of new applicants are not producing the necessary documents, said Kathleen Westcoat, president of Baltimore HealthCare Access.

"It's a nightmare for the local health departments," who only have 10 days to process new applications to the Maryland Children's Health Insurance Program and 30 days for renewals, said Cobb.

"Every jurisdiction is doing something very different" to cope with the problem, said Westcoat.

"We're following the rules, we're just giving people a little more time to get their documents together."

As long as current recipients of Medicaid are making a "good faith effort" to provide the necessary documents, they won't get cut off, said Lehman.

For the homeless, getting identification is extremely difficult because often you need to have identification in order to get it, said Kevin Lindamood, a spokesman for Baltimore-based Health Care for the Homeless.

"It ends up being this kind of circle of futility that's very difficult to break," he said.

The state health department is trying to educate providers, but Lehman acknowledged, "perhaps we need to do a better job."

Of the roughly 50,000 new Medicaid applicants in September, Lehman estimated that the state already has citizenship records for 58 percent of them, leaving only identity to prove.

But identity is very tricky to prove, especially for young children, said Westcoat. A passport is the only document that proves both citizenship and identity, but hardly any low-income children have that, she said.

Westcoat said some parent have taken their babies to the Motor Vehicle Administration to get photo identification. She worries about the cost of obtaining identification for multiple children, the time and effort it takes to retrieve such documents and the lapse in health care that they may experience in the interim.